1. Field of the Invention
The present invention relates to current-to-pressure converter apparatus.
2. Description of the Prior Art
Various electro-pneumatic transducers which convert an electrical signal into a pressure signal for controlling valves and the like have been used in the prior art. For example, Fischer Controls of Marshalltown, Iowa makes several models, typical of which is the Type 456 Electro Pneumatic Transducer. These devices utilize an armature for controlling a fluid flow, and which fluid flow in turn operates a feedback diaphragm controlling the bleed of a supply of fluid under pressure in atmosphere.
Another type of device which operates on a similar principle, but which uses mechanical feedback is called the E69 Series Current Pneumatic Converter Positioner made by the Foxboro Company of Foxboro, Mass.
Electrical feedback arrangements have also been used in some prior art electro-pneumatic transducers. Examples of these prior art devices are shown in U.S. Pat. Nos. 2,914,076; 2,930,430; and 2,941,723.
Other examples of control apparatus using fluid pressure signals are shown in U.S. Pat. Nos. 2,928,409; 3,063,422; 3,134,425; and 3,456,669. In particular, U.S. Pat. Nos. 3,063,422 and 3,456,669 show piezoelectric elements used as flappers to control pressure outflow from nozzles.